Method for production of cyanogen compounds



Patented May 6, 1924.

UN TED STATES IOOBD VON BIOHOWSKY, O1 GLENDALE, CALIFORNIA.

METHOD FOR PRODUCTION OI OYANOGEN COMPOUNDS.

Iii Drawing.

To all whom it may concern:

Be it known that I, Foono Von Bicnowcar, a citizen of the United States, and a resident of Glendale, county of Los Angeles, State of California, have invented a new and useful Method for Production of Cyanogen Compounds, of which the following is a specification.

My invention relates to improvements in methods for the production of cyanogen compounds, and in articular to hydrocyamc acid and the alkai metal cyanides, from furnace products containing the latter. In the carrying out of my invention I obtain excellent yields of cyanogen compounds under conditions previously thought most unfavorable and I obtain these excellent results, with a minimum of process regulations, in a simple, and yet exceptionally safe manner.

It has been known for a long time that alkali metal cyanides are quantitatively dccom osed into hydroc anic acid and. an alkai metal carbonate y the combined action of carbon dioxide and water: Beilstein Handbuch der Organischen Chemie, edition of 1893, vol. 1, page 1413: in accordance with the following general equation where R represents an alkali metal.

Recently this method has been proposed for the recovery. of cyanogen compounds from impure mixtures containing them. According to United States Letters Patent No.

1,385,335 the cyanide containing mass istreated with carbon dioxide and water the temperature being so regulated that polymerization of the hydrocyanic acid, which action is stated to be quite active at 3040 C., is avoided. In United States Letters Patent No. 1,385,336, this same polymerization of the acid is minimized by greatly fincreasing the rate of flow of the carbon dioxide gas over the mass to be treated. I

I have :now discovered that the hydiocyanic acid may be recovered in a practically theoretical amount and in a pure form from products containing pure or impure alkali metal cyanides such as for example the furnace products resulting from heatin together a nitride, a carbide and an a kali metal carbonate as described in my eopending application Serial No. 474,222, or from any other cyanide containing mass, providing the operation be conducted at below Application filed August 8, 1828. Serial 1T0. 658,111.

atmospheric pressure, and that CO and water vapor be present in excess of that required by theo Under these conditions no attention need paid to cooling the mass, as no visible polymerization results even at 40 C., and in addition the rate of carbon dioxide flow can be made quite low. To carr out my discovery it is only necessary to p ace the moist alkali metal cyanide containin mass in a suitable container, adapted to be c osed and equipped with a stirring device, to then evacuate the container to a barometric reading, of say, 20 inches of mercury, and allowing carbon dioxide to flow into the container at such a rate that the gau reading on the container is not noticeab y changed. The resulting hydrocyanic acid may be recovered from the exhaust gases from the vacuum pump, b condensation or else by absorption in Naol l solution, in solid NaOH or Na CO or in any other suitable alkaline reagent.

If desired the absorption in the solid N aOH or soda ash may take place under a reduced pressure so that the water which is set free escapes at a temperature which does not cause t e resulting NaCN to have a dark color.

It is also much safer to carry out the liberation and absorption of HCN under less than atmospheric pressure as any leakage in the apparatus will be from without toward the inside of the apparatus, and therefore no dan er to the workmen from the accidental in aling of the. very poisonous hydrocyanic acid can result.

I claim:

1. The method for recovering pure cyanogen compounds from materials cantaining them which consists in treating the materials with water and carbon dioxide under less than atmospheric pressure and in recovering the cyanogen compounds.

2. The method for recoverin pure cyanogen compounds from materia s containing them which consists in treating the materials with water and carbon dioxide under less than atmospheric pressure and in absorbing the hydrocyanic in an alkali compound of an alkali metal likewise kept under reduced pressure.

3. The method for recoverin pure cyanogen compounds from materia s containing them which consists in treatin the materials with water and carbon dioxi e and absorbing-the resulting hydrocyanic acid in sodium hydroxide, the entire ofieration taking place under less than atmosp eric pressure.

4. The method of recoverm pure cyanoen compounds from materia s containing 5 t he same, which consists in treating the materials with water in the liquid phase and carbon dioxide gas and. absorbing the resulting hydrocyanic acid in sodium hydroxide, the entire operation taking place under less than atmospheric pressure and under such temperature conditions and rates of flow as to avoid polymerization of the resulting products. v

FOORD VON BICHOWSKY. 

